BS 949-4:1990
Current
The latest, up-to-date edition.
Screwing taps Specification for metric ground thread taps: manufacturing tolerances
Hardcopy , PDF
English
06-29-1990
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National foreword
Brief history
Text of EN22 857
Specification
1. Scope and field of application
2. References
3. Basic data
3.1 Thread profile of nuts
3.2 Thread profile of tap
3.3 Tolerance classes of taps
3.4 Calculation of tap thread dimensions of classes
1, 2 and 3
4. Manufacturing tolerances on tap threads
4.1 Major diameter d
4.2 Pitch diameter d2
4.3 Minor diameter of tap d1
4.4 Tolerances on the half-angle alpha/2 of thread
4.5 Cumulative pitch error Tp over any number of
threads
5. Designation and marking of taps
6. Example of calculation of the dimensions of the
threaded portion of a tap
Annexes
A. Ground thread taps for ISO metric threads of
coarse pitch
B. Ground thread taps for ISO metric threads of
fine pitch
National appendix A
National appendix B
Cooperating organizations
Manufacturing tolerances on the threaded portion of taps for producing ISO metric threads of tolerance classes 4H to 8H and 4G to 6G. Valid for short taps specified in ISO/R 529 as well as any other kind of ground thread taps with the same diameters and pitches.
| Committee |
W/-
|
| DevelopmentNote |
Reviewed and confirmed by BSI, March, 2004. (11/2004) Also numbered as EN 22857 and ISO 2857 Supersedes 85/78210 DC and BS 949-1(1976) (10/2005)
|
| DocumentType |
Standard
|
| Pages |
28
|
| PublisherName |
British Standards Institution
|
| Status |
Current
|
This International Standard specifies the manufacturing tolerances on the threaded portion of taps for producing the ISO metric threads of tolerance classes 4H to 8H and 4G to 6G as defined in ISO/R 965-I to III (excluding, consequently, classes 7G and 8G considered as usually produced with ground thread taps).
It is valid for the short taps specified in ISO/R 529 as well as for any other kind of ground thread taps with the same diameters and pitches.
The internal threads produced with those taps are conventionally designated by the simplified denomination of “nut?? in agreement with the word used in ISO/R 965 for the general designation of all internal threads.
Annex A and Annex B give, for all threads with coarse and fine pitches, the manufacturing tolerances on the threaded position of taps for the following classes of nuts:
4H and 5H − 6H − 7H and 8H
| and | 4G and 5G − 6G |
| Standards | Relationship |
| EN 22857:1989 | Identical |
| ISO 2283:2000 | Long shank taps with nominal diameters from M3 to M24 and 1/8 in to 1 in — Reduced shank taps |
| BS 949-1:1976 | Screwing taps Specification for taps for ISO metric threads |
| BS 3643-1:1981 | ISO metric screw threads Principles and basic data |
| ISO 2284:2017 | Hand taps for parallel and taper pipe threads — General dimensions and marking |
| BS 5346:1976 | Specification. ISO metric trapezoidal screw threads |
| ISO 529:2017 | Short machine taps and hand taps |
| BS 949-3:1982 | Screwing taps Specification for taps for pipe threads (G series, R<sub>p</sub> series and R<sub>c</sub> series) |
| BS 949-5:1990 | Screwing taps Nomenclature and terminology |
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